A Chinese city of more than 21 million people is under a government lockdown ordered amid a new COVID-19 outbreak.

Residents of Chengdu, the largest city in China to be placed under lockdown since Shanghai residents were confined to their homes in April and May, are permitted to send just one person per day from their households to shop for necessities, CNBC reported.

The lockdown of the capital of the manufacturing hub in southwestern China took effect at 6 p.m. Thursday, a day after the city reported 157 COVID-19 cases, according to CNBC. The cable business news channel said it was unclear whether the restrictions would be lifted in Chengdu after mass testing ends on Sunday.

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Residents must have approval from neighborhood staff to leave their homes for hospital visits or other concerns, CNBC said, and a Volvo car plant was being shut down, although some manufacturing operations with “closed campuses” were exempted.

The start of the school year has also been delayed in Chengdu and some other Chinese cities, where measures that stop short of a lockdown have been taken, such as requiring working from home and closing swimming pools, subways and even an electronics market, The New York Times reported.

Last month, some 80,000 domestic tourists vacationing on China’s Hainan island better known as “China’s Hawaii” were trapped when the government suddenly imposed a COVID-19 lockdown that halted flights and other transportation.

Since Aug. 25, there have been more than 700 COVID-19 cases in Chengdu, The Times said, triggering action under China’s controversial “zero COVID” policy that calls for restricting the movement of people in an attempt to eradicate the virus, a policy other major countries have left behind to focus instead on limiting its impact.

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The Chinese government’s response to COVID-19 outbreaks is increasingly being criticized from within China. CNN reported Chengdu’s lockdown was preceded by several days of speculation on social media that spurred residents to stock up on groceries and other necessities.

A user of China’s popular messaging app, WeChat, was detained for 15 days and fined for what police said was “picking quarrels and provoking trouble,” through “provocative comments” described as causing panic and disrupting prevention efforts, according to CNN.